Returns previous cell or null if it is first cell in the grid.

<div class="definition">
     prevCell(index, colIndex, editable)
</div>

<div class="arguments">
    <table>
    <tr>
        <td>index</td>
        <td><b>integer</b>, record index</td>
    </tr>
    <tr>
        <td>colIndex</td>
        <td><b>integer</b>, column index</td>
    </tr>
    <tr>
        <td>editable</td>
        <td><b>boolean</b>, indicates if to return previous editable cell</td>
    </tr>
    </table>
</div>
Returns { index, colIndex } object or null.

<h4>Description</h4>

This method returns you previous cell or previous editable cell. It will advance to the previous row if any. If there is no
previous cell, it will return null. Will skip hidden columns.
<div style="height: 10px"></div>

The first argument <span class="argument">index</span> is the index in the <a class="method" href="w2grid.records">.records</a>
array. The second argument <span class="argument">colIndex</span> is the index in
the <a class="method" href="w2grid.columns">.columns</a> array.
<div style="height: 10px"></div>

If you have grid defined in the following way:
<textarea class="javascript">
let grid = new w2grid({
    name: 'grid2',
    columns: [
        { field: 'recid', text: 'ID', size: '50px' },
        { field: 'lname', text: 'Last Name', size: '30%', editable: { type: 'text' } },
        { field: 'fname', text: 'First Name', size: '30%', editable: { type: 'text' } },
        { field: 'email', text: 'Email', size: '40%', editable: { type: 'text' } },
        { field: 'sdate', text: 'Start Date', size: '120px', editable: { type: 'date' } },
        { field: 'edate', text: 'End Date', size: '120px', editable: { type: 'date' } }
    ],
    records: [
        { recid: 1, fname: 'John', lname: 'doe', email: 'vitali@gmail.com', sdate: '1/3/2012' },
        { recid: 2, fname: 'Stuart', lname: 'Motzart', email: 'jdoe@gmail.com', sdate: '2/4/2012' },
        { recid: 3, fname: 'Jin', lname: 'Franson', email: '--', sdate: '4/23/2012' },
        { recid: 4, fname: 'Susan', lname: 'Ottie', email: 'jdoe@gmail.com', sdate: '5/3/2012' },
        { recid: 5, fname: 'Kelly', lname: 'Silver', email: 'jdoe@gmail.com', sdate: '4/3/2012' },
        { recid: 6, fname: 'Francis', lname: 'Gatos', email: 'vitali@gmail.com', sdate: '2/5/2012' }
    ]
});
</textarea>

You can do:
<textarea class="javascript">
w2ui['grid2'].prevCell(5, 3, true);
</textarea>